The present invention relates to an improvement in a reel lock mechanism for a tape cassette.
In a tape cassette for use with a VTR or the like, there is provided a reel lock mechanism for preventing slack of a tape when the tape cassette is in an unused condition.
FIG. 7 shows an example of such a reel lock mechanism a in the conventional tape cassette.
Referring to FIG. 7, reference character b designates a lower half of a cassette case, and reference characters c and c' designate lower flanges of a supply tape reel and a take-up tape reel around which a magnetic tape d is wound. The lower flanges c and c' are formed with a plurality of outer circumferential teeth e and e', respectively.
Reference character f designates a reel lock member comprised of a main portion g and two lock portions h and h' projecting from the main portion g. The reel lock member f is biased in a direction as depicted by an arrow A by biasing means (not shown).
The lock portions h and h' are formed of an elastic material, and they are normally engaged with the teeth e and e' of the lower flanges c and c' to thereby lock the tape reels.
In other words, while the flanges c and c' are permitted to rotate in opposite directions of stretching the magnetic tape d as depicted by arrows B and B', the flanges c and c' are restrained from rotating in the directions of slacking the magnetic tape d by means of the lock portions h and h'.
However, in the conventional reel lock mechanism as mentioned above, when a force depicted by an arrow F in FIG. 8 due to vibration or the like is applied to the flange c of the supply reel, for example, the reel lock member f is moved in a direction depicted by an arrow C by this force F. As a result, the lock portion h' comes into disengagement from the tooth e' of the flange c' of the take-up reel.
Under the above condition, the take-up reel is allowed to rotate not only in the stretching direction of the tape d but also in the slacking direction of the tape d. Accordingly, the tape d is slackened to cause jamming (confused winding) of the tape, for example.
To cope with this problem, referring to FIG. 9, it is considered that click portions j and j' are formed at substantially middle positions of two lock portions i and i', respectively, so that when the force F is applied to the supply reel, the lock portion i is bent at the click portion j so as to escape the force F.
However, in the construction shown in FIG. 9, there is a problem regarding a strength of the click portions j and j'. That is, there is a possibility that the release of the locked condition cannot be reliably prevented dependently upon a magnitude of the force F to be applied.